DESCRIPTION (applicant's abstract): This proposal examines the interaction between the brain and a stressful environment during the developmental period of adolescence. It is well documented that perinatal stressors can affect brain development resulting in long-term neurobiological and behavioral consequences. However, little is known about the biological consequences of stress in adolescence. There are reports that adolescents between 12-15 are ranked third in victimization rate while adolescents between 16-19 are the most victimized group in the population. In an animal model, peripubertal or adolescent male hamsters exposed to the stress of threat and attack from larger hamsters present with altered agonistic behavior as young adults when compared to their sibling controls. In addition, adult animals with a history of adolescent stress have altered brain chemistry, specifically, the arginine vasopressin (AVP) and serotonin (5-HT) innervation to the hypothalamus involved in the regulation of agonistic behavior. This work asks three questions: (1) how has adolescent stress affected the AVP and 5-HT systems; (2) are the behavioral and neurobiological changes caused by stress in adolescence different from those caused by stress in adulthood; and (3) are the changes in neurobiology and behavior from adolescent stress permanent? Stress-induced changes in the AVP and the 5-HT systems are determined by measures of gene transcription, receptor binding, and neurotransmitter release with microdialysis; the behavior and neurobiology of siblings exposed to stress during adolescence or adulthood are compared to age matched sibling controls; and animals stressed in adolescence are examined over several months for recovery of behavior and neurobiology. This work will help understand the effects of stress in adolescence and the ability of the brain to recover from insult at this potentially vulnerable period of development.